Both the ThunderJet Envoy - Northern Edition 2009 and the ThunderJet Havasu 2010 are modified-V designs, both built in aluminium, so the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
Both boats share a closely matched power ceiling - 250 hp for the ThunderJet Envoy - Northern Edition 2009 and 250 hp for the ThunderJet Havasu 2010. Real-world performance will come down more to which motor is actually bolted on, its load at the time, and whether it's a 4-stroke or 2-stroke setup. Both carry nearly identical fuel loads - 48 gal and 50 gal - so range won't be a tiebreaker here.
For family outings this is probably the sharpest distinction between the two. The ThunderJet Havasu 2010 is rated for 6 passengers, while the ThunderJet Envoy - Northern Edition 2009 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the ThunderJet Havasu 2010 could be the deciding factor.
Bottom line: Choose the ThunderJet Havasu 2010 if your priority is putting more people on the water - it handles 6 passengers and at 20,0 ft it has the deck room to back that rating up comfortably. The ThunderJet Envoy - Northern Edition 2009 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.